It is well known for the transmitter and receiver of a radio frequency transmission system to be configured to either make use of the same antenna or have separate transmit and receive antennas that are placed in close proximity to each other. The signal interference problems associated with such transmission system configurations are also well known in the art. One serious problem occurs when a portion of the signal generated by the transmitter "leaks-through", to the receiver and mixes with the received signal. When the leak-through signal is in the passband of the receiver, the likelihood of degradation in receiver performance substantially increases. Accordingly, there is need for transceiver and antenna isolation systems (e.g., directive antennas, circulators, balanced networks and hybrids, filters) and interference cancellation systems (e.g., leak-through signal cancelers).